We analyzed seven patients with beta-thalassemia intermedia presenting with congestive heart failure secondary to pulmonary hypertension. This condition has been recognized only recently as part of the clinical spectrum of beta-thalassemia. Our group of patients included two men and five women with the clinical picture and laboratory data typical of beta-thalassemia intermedia. The mean age was 37.7 +/- 11.4 years, mean hematocrit value was 28.5 +/- 1.8%, mean number of transfused blood units was 171 +/- 153, and mean serum ferritin levels were 4,428 +/- 2,006 ng/mL. All but one of these patients had undergone splenectomy. Common findings of the investigative procedures include the following: dilation of the main pulmonary artery and cardiac enlargement in the chest radiograph; signs of right ventricular hypertrophy in the ECG; and dilated right ventricle with good left ventricular function in the echo study. Right heart catheterization showed the pulmonary systolic pressure to range from 55 to 90 mm Hg (74.1 +/- 10.3), pulmonary diastolic pressure from 25 to 50 mm Hg (37.7 +/- 8.7), mean pressure from 35 to 60 mm Hg (49.7 +/- 7.9), and pulmonary vascular resistance from 267 to 667 dynes.s.cm-5. Pulmonary capillary wedge pressure was within the normal range of values. The pathophysiologic condition of pulmonary hypertension in these patients is most probably associated with beta-thalassemia. There are mechanisms that increase cardiac output and at the same time restrict the pulmonary vascular bed. The results of this study imply that treatment decisions should be reconsidered for such patients.